If your fish tank isn't broken I wouldn't fix it.
The system is for someone who wants to setup a new tank and not have to wait or someone that is having trouble with their system.
Large fish wholesalers tend to have problems with nitrates because of the large volume of fish and corals they carry. The high fish load and waste poses a threat to the corals. Therefore, it is advantageous for wholesalers to sell, sell, sell or they will lose profit. Otherwise, they throw the bleaching corals in to the potluck bin/tank for cheap.
The system can be adapted for fish only (full carbon) and coral tanks (less carbon) according to the simple formula.
Ca, Mg, trace elements, and pH can be manually adjusted or use pH rock ~ calcium reactor media.
Please keep the questions coming.